Refrigerator defrost termination control system



Dec. 1M1, 1956 H. TILLMAN 2,773,354

REFRICERATOR DEFROST TERMINATION CONTROL. SYSTEM Filed May 4, 1955 llllIHlll d Il f n l #VVE/WUR HARRY L. TML/WAN F/GZ ATTORNEY United States Patenti i REF-RIGERA-TORU DEFROST TERMINATION CONTRL SYSTEM Harry'4 ILrTilIman, ,i Evansville, Ind., assigner, by mesne assignments, to Whirlpool-Seeger Corporation, a corporation of 'Delaware Application JMay 4; 1953, Serial No. 352,918l

3 rClaims.- (Cl.y 62-2)A rllltiis invention relates'generally to refrigerator defrost systems; and: vmore specifically to L an: improved ,refrigeratori? defrost' termination control `system.wherein a gas lfilled capillary tubeJ and l af bellows comprises a portion of 1` the control system;

Thewuseloftalgaseiilled' capillary tubeand a` bellows irrfay refrigerator defrost termination control systerrr to' detect a certain temperatureyrise' of. the refrigerator evaporator" to indicate i the completion i of'` the '1 defrosting of 1the evaporator,` and to actuate the bellwsf to Lterminate.v

theadefrostcycle, gives riseto a'lnurnberfofrproblerns;`

InlI-a systemof this nature` itlhasbeen found` thatA the coldest` point'fonr thenc-apillary tube andl'th'e' bellowsis. theicontrolling point This resultsfromthetfact that the 'pressure fexertedby' the bellows -will :bea :direct func= tionvof theternperature of the' gas` within` theucapi-llarytube and .the `bellows-at the coldest point thereof. This is a" disadvantage: inf that refrigeratorfevaporators are usuf` ally fheated `by electrical .l heatingf coils, and. often, during..`

theadefrostingA cycle; especiallyl when ithe interior` ofthe. refrigerator cabinet has beenzmaintainedat af compara# tively low temperature, ,the evaporator surfacelsmay; become:` considerably warmer than'I the: cabinet interior.

Thus, the. closedj end? of -i the. capillary tube;` which ist` in" contact with.` the` evaporator surface; will'.` betfat a@ temperature/substantially above other portionsl of the capil-i larytube and the bellows.y In this casesomefother point alonglthe capillary tubeor` thebellows willrbe the-conf ltrolling point.` for 'the termination; of the'l defrostf cycle.

The` defrostcycle will? continue until al1 l points lalng` theicapillarytubeand the bellows. are above fsthe cutaoi temperature. By this time'the temperature: oftthe `levap`- orator'imaybesuch that any frozenv foodsl whichrmayfbe` positioned within the evaporatorwill .bemeltedl' If'anf attemptisgmade `toovercome this 'disadvantage by a* loweringf" ofthez cut-on temperature of the-termination' lcon trolnsystem, the defrostl cycle willfbe terminated in a shorter. period i of*` time',` when the refrigeratorcabinet i is operated at a comparatively high temperature; with the resultrthat theevaporatorl will not becompletelydefrosted, since at higher cabinet temperatures` the` same or even longer. periods of fdefrosting' may. b'erequiredl to melt all of theice formedonithe evaporator.

Therefore, it is an important object ofi thisrinvention to provide a' refrigerator.` defrost termination control systemcomprisinga capillary tubev and'al bellowsv'wherein the'end ofthe capillary tubeiwill at all times remainithe controlling point.

Itl is. a furtherobjectof this invention to providea refrigerator. defrost termination control systemlwhich will efficiently permit the use of a low cut-oif temperature for theterminationof the defrost-cycle.

Itis afurtheriobject of this inventionto provide av refrigerator defrost termination control system which will permit i effective rdefrosting `at `comparatively high' or lowcabinet: temperatures.

It is-afeature of'this invention that a=novel water 2.o container isImountedinicooperation with an-evaporatorf surface, a capillaryitube and. a' bellows:

It is afurtherv featurezof `this invention"thatdefrost water is-` used to=constantly `maintain the novel Water container filled;

Other, objects and features` of` the present invention will be apparenet uponfa perusal of the following speci-r iication and drawing `of which Figure l is apartial\cross-sectional side View ofwaJ refrigerator cabinet embodying the present invention;` and;

Figure 2 is a front plan view of therefrigerator cabinet shown in Figure l with the refrigerator door re moved.

The present embodiment is the preferredembodiment butit is to be understood that ohangescan be=m`adei11 the rpresent embodiment by one'skilled Vintthe` art with'-i outdepartingv from the spirit andscope of thisinven-V tion:

For a` detaileddescription of theinvention referenceA is made to the` dra'wing wherein a refrigerator cabinet 5 is shown with a refrigerator door 'mounted over theopen sidethereof to define a food "compartment 7`.` The refrigerator lcabinet 5 andthe refrigerator door 6may be of any typewell known in the art.' A rectangularly shapedirefrigerator evaporator 8 is mounted within the upper `portion of the food compartment 7 bymeans of' the mounting means 9. 'The refrigertaor evaporator 8y and the mounting means 9 may be of any type'well' known in the art. The evaporator 8, as shown, comprisesL a length of serpentine `tubing 10`mounted to the evapora'- tor in thermal contact therewith. As is wellknown in the art,` the evaporator tubing-10 serves to conductrefrigerant therethrough to coolthe evaporator surfaces and to cool the foodcompartment 7. The ends of the serpentine tube 10"are connected intothe remainder of a conventional refrigerator system (not shown). Such a conventional refrigerator system'includes control means for causing the food'compartment' 7 to be maintained4 at different ranges of temperatures. The space 11 disposed within the evaporator 8A comprises the conventional refrigerator freezer compartment; Frozen food may be placed within the compartment 11; upon the surface. 12,` andlupon' therack 13, and further` in `thermal contact wit-h the two sidewalls 14. Frozen foods so placed will be maintained at freezing ltemperatures by` the evaporator 8.

As is-well'known in' theart, frost will form upon the. surfaces of the evaporator after a certain period of op; eration thereof. To remove this .accumulation of frost it is necessary to periodically defrost the evaporator, and. to accomplish thispurpose a conventional heating ,coil 15-is provided, and'is` mounted in thermal contact with4 the outer-surfaces of the evaporator 8. The ends 16 yof the heating `coililSare connected to any conventional power supply and'defrost cycle initiating means (not shown). Thus when `the defrost cycle is initiated, ,current wiiliflow through the heatingcoil 15 toh'eat the coil'15ll The heat from the heating coil 1S will in turn be con-V ductedto the surfaces ofthe evaporator S to meltthe frost laccumulations therefrom. Should the heatingjcoil 15 be energized for a period longer than.necessaryto melt the frost, any frozenfoodswithin compartment 11 may be melted. Within a'portion of the heating coil "15," a switch 17 is connected. The switch 17` comprises:a` stationary contact 18 and a movable contactarrn'19. The contact 181 and the contact arm 19"are biasedto a normally closed position by the spring 20.` Thus, it" can beseen that when themovable contact'arm 19 is moved from contact with the contact 18, the' heating' circuit", 15`f for' the defrosting of the' evaporatoris opened."

To open and close the switch 17, a bellows element 21 is provided. The bellows 21 is so formed as to expand and contract with changes of the internal pressure therein. To provide means for changing the pressure within the bellows 21 a length of tubing 22 is provided. One end of the length of tubing 22 is connected into one side of the bellows 21. The other end of the length of tubing 22 is sealed, and the length of tubing 22 and the bellows 21 are filled with a gas, so that when the length of tubing 22 is cooled, the gas disposed therein will cool to cause the pressure therein to decrease, to cause the bellows 21 to contract. Further, if the length of tubing 22 is heated, the gas disposed therein will expand, to in turn cause the bellows 21 to expand. The other side of the bellows 21 is pivotally connected to the movable contact arm 19 as can easily be seen in Figure 1, so that any expansions and contractions of the bellows 21 will cause a movement of the contact arm 19 Iagainst and aided by the bias of the spring 20, respectively. The pivotal connection of the bellows to the arm 19 is made adjustable by any means well known in the art so that the cut off temperature of the termination control may be Varied. The length of tubing 22 is lixedly maintained adjacent to one side of the evaporator 8 by means of the mounting means 23. The closed end of the length of tubing 22 is disposed within a container 24.

The container 24 is generally shaped as a four sided trough, and the top thereof is open. The container 24 is mounted in thermal contact with one side of the evaporator 8 by means of the mounting means 25. The container 24 is filled with water or ice dependent upon the temperature of the evaporator. Since the container 24 isv mounted against `one side of the evaporator and since the topvof the container 24 is open, the container 24 will be maintained full of water by defrost water running from the outer surfaces of the evaporator 8 during the defrost cycle. Therefore, during the refrigeration cycle the water disposed within the container 24 will be frozen with the result that the closed end of the length of tubing 22 will be encased within a block of ice.

To describe the operation of the instant invention it will be rst assumed that the food compartment 7 is being maintained at a comparatively low temperature. The termination control may be adjusted to a low cut-olf temperature. The closed end of the capillary tube 22 which is encased in the block of ice will be at the lowest temperature, and the closed end of the capillary tube 22 will remain at the lowest temperature until the block of ice is completely melted. The time required to melt the block of ice will be ample for proper defrosting and the low cut-olf temperature will prevent the evaporator from becoming excessively warm. Thus, after the ice in the container 24 has melted, the water may be heated to some temperature such as 40, at which time the gas within the capillary tube 22 and the bellows 21 will ex? pand sufficiently to move the contact arm 19 from contact with the contact 18 to stop the defrost cycle.

When the cabinet temperature is maintained at a comparatively high temperature, the bellows and a large portion of the capillary tube 22 will be at a substantially higher temperature than the closed end of the capillary tube 22. The block of ice about the closed end of the capillary tube 22 will prevent the end of the closed end of the tube 22 from increasing above the temperature at which the ice will melt until all of the ice within the container 24 has melted. This delay action will provide ample time for proper defrosting of the evaporator at the comparatively high cabinet temperatures.

Having described the invention in detail what is considered new and desired to be protected by Letters Patent is:

1. In a refrigeration system having an evaporator and a means for defrosting said evaporator, a defrost termination control comprising a container mounted to one Wall of said evaporator in thermal contact therewith, a w

quantity of ice disposed within said container when said evaporator is operating on a refrigeration cycle, said container formed in the shape of an open trough so that any water frozen therein can expand without breaking said container and so that any water and ice lost therefrom by evaporation is replaced by defrost water flowing over the surfaces of said evaporator and into said troughshaped container, a length of tubing being closed at one end thereof, a bellows, the other end of said length of tubing being connected to one end of said bellows, a.

certain amount of a gas disposed within said length of tubing and said bellows, said gas of an amount sucient to cause the operation of said bellows on an expansion thereof responsive to a rise in temperature of the entire length of said length of tubing some temperature above the freezing temperature of water, said closed end of said length of tubing being disposed within said container whereby said closed end of said length of tubing is maintained at a temperature below the freezing temperature of water when said means for defrosting said evaporator is operating until said ice disposed within said container is melted, and means connected to the other end of said bellows and operating responsive to the operation of said bellows for terminating said means for defrosting said evaporator.

2. In a refrigeration cabinet having an evaporator disposed therein which is selectively operable to one position to maintain said cabinet at a low temperature and selectively operable to another position to maintain said cabinet at a high temperature and having means for defrosting said evaporator, a defrost termination control comprising a length of tubing being closed at one end, a bellows, the other end of said length of tubing being connected to one end of said bellows, said length of tubing and said bellows being positioned within said cabinet, a certain amount of gas disposed within said length of tubing and said bellows, said gas of an amount sufficient on the expansion thereof to cause the operation of said bellows responsive to a heating of said length of tubing and said bellows along the entire length thereof above a certain predetermined temperature above the freezing temperature of water, and means for preventing the closed end of said length of tubing from rising above said certain predetermined temperature for a predetermined length of time when said cabinet is maintained at said low temperature and for maintaining said closed end of said length of tubing below said certain predetermined temperature for a predetermined length of time when said refrigerator cabinet is maintained at said high tem perature, said last mentioned means comprising a container, said container mounted in thermal contact with one surface of said evaporator, a quantity of ice disposed within said container, said container formed in the shape of an open trough so that any water and ice lost therefrom by evaporation is replaced by defrost water flowing over the surfaces of said evaporator and into said troughshaped container, and said container being so positioned that said closed end of said length of tubing is positioned within 'said container, and means operating responsive to the operation of said bellows for terminating said means for defrosting said evaporator.

3. In a refrigeration cabinet, an evaporator disposed within said cabinet, means selectively operable to one position for causing said evaporator to maintain said cabinet at a low temperature and selectively operable to another position for causing said evaporator to maintain said cabinet at a high temperture, means operable to defrost said evaporator, a defrost termination control comprising a length of tubing being closed at one end, a bellows, said length of tubing and said bellows being positioned within said cabinet, the other end of said length of tubing being connected to one end of said bellows, a certain amount of gas disposed within said length of tubing and said bellows, said gas of an amount sutiicient on the expansion thereof to cause the operation of said bellows responsive to a heating of said length of tubing and said bellows along the entire length thereof above a certain predetermined temperature above the freezing temperature of water, and means for preventing the closed end of said length of tubing from rising above said certain predetermined temperature for a predetermined length of time when said cabinet is maintained at said low temperature and for maintaining said closed end of said length of tubing below said certain predetermined temperature for a predetermined length of time when said refrigerator cabinet is maintained at said high temperature, said last mentioned means comprising a container, said container mounted in thermal contact with one surface of said evaporator, a quantity of ice disposed Within said container, said container formed in the shape of an open trough so that any water and ice lost therefrom by evaporation is replaced by defrost water owing over the surfaces of said evaporator and into said trough-shaped container, said container being so positioned that said closed end of said length of tubing is positioned within said container, and means operating responsive to the operation of said bellows for terminating said means for defrosting said evaporator.

References Cited in the file of this patent UNITED STATES PATENTS 1,942,412 Dienner Jan. 9, 1934 2,066,235 Smilack Dec. 29, 1936 2,187,258 Wood Jan. 16, 1940 2,444,593 Davis July 6, 1948 2,635,439 Philipp Apr. 21, 1953 

